Pebble heater process and apparatus



May 7, 1957 M. o. KxLPATRlcK PEBBLE HEATER PROCESS AND APPARATUS 2 Sheets-Sheet 1 May 7, 1957K M. o. KILPATRICK PEBBLE HEATER PROCESS AND APPARATUS 2 Sheets-Sheet 2 Original Filed July 1'?, 194'? HEATER 6 7 .25 :ozmno 9 3 8 u 3 lvl .o .m 5.23 w A o e u 5 m m CONTROL AIR INVENTOR. M o. KILPATRICK BY w44 ATTORNEYS United States Patent O PEBBLE HEATER PROCESS AND APPARATUS Myron 0. Kilpatrick, Bartlesville, Okla., assignmto Phiilips Petroleum Company, a corporation of Delaware Continuation of application Serial No. 761,696, `luly 17, ggso This application April 3, 1953, Serial No.

This invention pertains to improved pebble heater apparams and to operation and control of pebble heater apparatus in performing hydrocarbon conversions in the vapor phase. A `specific aspect of the invention relates to the conversion of paraffnic hydrocarbons to olens.

This application is a continuation of application Serial No. 761,696, filed July 17, 1947, now abandoned.

The type of operation and apparatus with which the invention is concerned involves circulating a continuous lluent mass of refractory pebbles thru a series of vertically arranged chambers comprising a pebble heating chamber, a conversion chamber, and a relatively narrow interconnecting neck or throat. That portion of the pebble mass descending thu the heater is heated to a suitable predetermined temperature substantially above a desired conversion temperature and the thus heated pebbles pass thru the neck or throat to the conversion chamber where they are contacted directly with a desirable hydrocarbon feed gas for a suitable contact time to effect the desired conversion. The pebble mass descends thru the bottom of the conversion chamber and is fed at a regulated rate to an elevator which transfers the pebbles to an inlet at the top of the pebble heater for reheating and passage thru the conversion zone.

This invention encompasses certain methods and ap paratus for the operation and control of a pebble heater unit in hydrocarbon conversion operations. The claims annexed hereto and forming a part of the Specification point out with particularity the novel features of the invention.

The term pebble as used thruout the specification denotes any solid refractory material of flowable form and size which can be utilized to carry heat from one zone to another. Pebbles are conveniently substantially spherical and are about 1A; inch to about 1 inch in diameter with the preferred size for high temperature processes about 3/a inch. Pebbles must be of refractory material which will withstand temperatures lat least as high las the highest tomperature attained in the pebble heating zone. They may be of ceramic, metal, or other refractory materials. Pebbles constituted of alumina, beryllia, silicon carbide, stellite, periclase, zirconia, and mullite in adrnixture with each other and/or with other materials when properly fired serve very well at high temperatures, some of them withstanding temperatures up to about 4G00n F. Pebbles may be relatively inert or catalytic in any given process.

The objectives of the invention include the following:

To provide a process and apparatus for the conversion of hydrocarbons permitting accurate control of the extent of conversion.

To provide a method and apparatus for conversion of hydrocarbons to more desirable materials with automatic controls permitting safe operation and efficient production of an eEluent of predetermined characteristics.

To provide for automatically controlled operation of a pebble heater unit in the conversion of hydrocarbons and arrangement of apparatus to etect such control.

2,791,545 Patented May 7, 1957 ice To provide a method and apparatus for more flexible control of pressure in the conversion zone in a conversion process.

To provide a method and apparatus for substantially preventing the mixing of combustion gases and product gases in a hydrocarbon conversion process in a pebble heater installation.

To provide protective control means in the operation of a pebble heater unit in a hydrocarbon conversion process.

Other objects of the invention will become apparent from a consideration of the accompanying disclosure.

ln the conversion of hydrocarbons in a pebble heater unit, especially in the cracking of light hydrocarbons, the matter of controlling the depth of conversion or cracking offers considerable diicnlty. One of the features of novelty of the invention resides in the control of the extent of conversion or the character of the conversion zone effluent by regulating the heat input to the conversion chamber of a pebble heater unit in accordance with the specific gravity of the conversion zone effluent. For example, it is found that in the cracking of light hydrocarbons to produce olens, the specific gravity oi' the cracked effluent offers the only accurate criterion for determining the extent or depth of cracking. 'lhe accompanying drawing and description point out the means and methods by which rsuch control is effected together with other novel features of the invention.

As an aid to understanding of the invention, reference may be had to the accompanying drawing which illus trates preferred embodiments of the invention.

Figure I shows a diagrammatic arrangement of appa ratus for effecting controlled conversion of hydrocarbons according to the invention.

Figure II is a sectional elevation of a pebble heater unit such as that illustrated in Figure I and illustrating an additional method of control.

Referring to Figure I, numerals 11 and 12 designate a pair of refractory lined chambers serving as a pebble heater and a reactor, respectively, being disposed in substantially vertical alignment and connected by a throat 13 in order to facilitate the easy iow of pebbles thru the heater, throat, and reactor. Numeral 14 designates a pebble inlet to the heater while 15 indicates a pebble outlet from the reactor. In operation, pebbles admitted to heater 11 are heated by direct contact with hot combustion gas as they pass downwardly thru the heater. A stream of hot pebbles passes thru throat 13 into reactor 12 where the pebble stream expands and comes into contact with a desirable hydrocarbon feed gas being passed upwardly thru the reactor. The pebble stream converges in outlet 15 and passes thru conduit 16 to pebble feeder 17 which feeds pebbles at a controllable rate to the elevator 18. Elevator 18 lifts the pebbles to conduit 19 which leads back to the inlet 14 to heater 11.

During operation of the unit, a suitable fuel is fed to burner 21 thru line 22 where it is mixed with air admitted thru line 23 under the force of blower 24. lnstrument 20 is a meter for measuring and recording fuel flow in line 22. Hot combustion gas produced in burner 21 passes upwardly thru heater 11 in direct contact with descending pebbles and passes out thru stack 2S. Any desirable hydrocarbon feed gas is metered thru line 26 by rate of flow controller instrument 28 which controls valve 27. This feed gas which may be admixed with steam admitted thru line 29 under the control of valve 31 is passed upwardly thru reactor 12 in direct contact with descending hot pebbles under conditions of pressure, contact time, and temperature which insure the desired conversion. Eflluents from reactor 12 pass thru line 33 to quench tank 34.

The pressure maintenance system around hydrocarbon blower 41 is one of the important features of the invention. In hydrocarbon conversion processes, it is genen ally important to maintain at all times relatively constant pressure in the reaction zone and to simultaneously main-- tain pressure in the elliuent line at least as great as atmosphcric so as to prevent leakage of air into the system. In order to maintain desirable pressures, the speed of blower 41 is automatically regulated by control 42 which is a conventional pressure controller recorder in communication with eliiuent line 39 upstream of blower 4l and controlling valve 43 in steam line 44 which supplies steam to the turbine operating blower 41. in this mank ner, under normal operating conditions. the speed of blower 41 is regulated to maintain constant suction prcssure on line 39 and hence. on reactor 12. Under ab normal operating conditions such as sometimes occur in hydrocarbon conversion processes, suction pressure in line 39 may tend to fall below a desirable minimum when the speed of blower 41 is reduced to n minimum operable limit and in this case pressure recorder controller' 45 bcgins to operate by opening valve 46 in line 47 permittirg7 part of the hydrocarbon stream to bypass and discharge back to line 39 upstream of the blower and in this manl ner maintaining a desirable pressure in line 39 upstream of blower 4l. Under extreme conditions where blower 4l and bypass line 47 are unable to maintain suitable pressure in line 39, pressure controller recorder i8 operu ates valve 49 in line 51 to admit sutiicient pressure maiutenance gas to maintain a predetermined minimum pressure in line 39, In this manner, with a given flow of feed to reactor l2. by a series of successively and cumulatively functioning steps, including varying the suction pressure on the product stream within a limited range in a suction zone in blower 41. and when a certain minimum pressure is reached in line 39, recyling a portion of the product stream from downstream of blower 4l to lin-c 39, and when a certain minimum pressure is again reached admitting a separate stream of pressure maintenance gas to line 39. the maintenance of a desirable pressure in line 39 is assured under all operating conditions.

A meter 52 in line 40 records the amount of product gas going to the compressors. Pressure controller rccorder 53 operates valve 54 in line S5 to regulate pressure in line 4i) by venting hydrocarbon gas to flare.

A temperature controller recorder 56 in communication with line 39 just downstream of quench tank 34, controls valve 37 in line 36 to regulate the amount of water admitted to quench tank 34, thereby maintaining; :i constant temperature in the quenched product stream. The temperature in line 39 may suitably vary anywhere between about 60 and about 200 F. depending upon the particular process and the construction of blower 4l. A pressure controller 57 in communication with line 36 operates valve 58 in line 59 to admit an emergency supply of water to line 36. in case the usual supply in lint.` 36 fails.

Steam at about 250 pounds pressure is supplied thru line 61 under the control of valve 70 operated by pressure controller 69 for distribution to the system where needed. Steam is metered to line 62 thru meter 63 under control of valve 64 which is manually operated to admit steam as a blocking gas to conduit 16, thereby preventing the flow of gases from reactor l2. Likewise, steam is metered thru line 65 thru meter 67 under the control valve 68 to throat 13 to serve as a blocking gas between heater 11 and reactor 12. In some hydrocarbon con version processes, steam is desired in admixture with the feed gas and this is provided where desired thru line 29 which is controlled by valve 31 operated by a rate of flow controller 71.

Under emergency conditions, steam is admitted to line 26 by valve 74, passing via lines 72 and 73, to purge rc actor 12 of hydrocarbon gas. Valve 80 supplies steam to fuel line 22 in order to purge heater 11 of hydrocarbon and combustion gases when it is necessary to shut off operation of the unit. This constitutes one of the import4 ant safety features of the invention. When processing hydrocarbons at extremely high temperatures, it is irnperative to remove hydrocarbons from the reaction zone of a pebble heater when the ow of hydrocarbons is inter'- rupted or when the ow of pebbles is interrupted because prolonged contact of the hydrocarbons with hot pebbles results in substantially complete cracking and excessive carbon deposit on the pebbles. It is found that under adverse conditions of this nature, pebbles become so carboned up that the mass of pebbles in the reactor become agglomerated and ceases to ow, thus, requiring a serious shut down and dismantling of the reactor in order to remove the coke pebbles. The automatic purging of the reactor in order to prevent such an oper-.ning difficulty is described hereinafter.

ln a hydrocarbon conversion process using a given contact time, amount or extent of conversion is dependent on the amount of heat supplied to the gas being processed. ln a pebble heater unit, the amount of heat dclivered to the reaction zone can be varied by increasing the temperature of the incoming pebbles and/or increasing the rate of ow ofthe pebbles thru the reaction zone. The apparatus of Figure l is designed to control thc amount of heat supplied to the reaction zone oy varying the temperature of the pebble stream entering said zone in response to variations in the specific gravity of the etlinent from the reaction zone from a suitable predetermined specific gravity. A gravitometer controller 76 in communication with product line 39 and valve 77 in fuel line 22 is responsive to variations in the specie gravity of the product stream. An increase in the specific gravity over the specific gravity of a desired product indicates that the charge gas is not being converted to the desired extent and gravitometer controller 76 opens valve 77. thereby increasing the amount of fuel passed to burner 21 which raises pebble temperature and with a given pebble How rate, increases the heat input to reactor 12` In this manner, the gravity of the product is brought to a predetermined value and assures a uniform product.

A gravitometer is an instrument which is designed and constructed to give an automatic and continuous reading of the gravity of the gas passing thru it as compared with air at standard conditions. The instrument is designed to compare the weight of a column of the gas of unknown gravity with the weight of a column nf air of equal height. Since the specic gravity of air is the standard and is unity, the specific gravity of the gas being measured is expressed in relation to air or unity. For instance the gravitometer-controller disclosed herein, when sct to maintain a specific gravity of 0.70 in cracking the ethane-rich hydrocarbon stream hereinafter described, maintains the specific gravity of the ciuent in the range ol" 0.695 to 0.705 by controlling the heat input to the cracking chamber. In other words, the gravitometercontroller utilized in the pebble heater unit of the invert tion makes a direct comparison ofthe weight of the hydrocarbon effluent with the weight of an equal volume of air under standard conditions and thru the controller device varies the conditions in the cracking chamber so as to maintain the optimum predetermined specilic gravity.

Varying the supply of fuel to burner 21 also varies the amount of air required for complete combustion of the fuel. There are two methods of controlling the amount of air admitted thru line 23. A constant amount of air which is adequate to support complete combustion under all conditions of operation may be supplied or the amount of air forced thru line 23 may be varied in response to variations in the amount of fuel admitted thrn line 22. The arrangement shown in Figure I provides for varying the air input in response to variations in the fuel input. Air blower 24 is operated by a steam turbine having n steam line 78. A pressure or rate of ow controller 79 in communication with fuel line 22 and with valve 81 in line 78 regulates the speed of the turbine driving blower 24 in response to variations in pressure or flow rate in line 22, thereby maintaining an air supply commensurate with the fuel supply to burner 21. A butterfly check valve 82 in line 23 serves to prevent any back ow of combustion gases from the preheater chamber or burner into the air blower. This valve is activated by oil pressure from the turbine governor in such a manner that the valve is snapped closed when the blower speed falls below a predetermined minimum.

In order to prevent overheating and possible fusion of the pebb-les or damage to the refractory lining of the heater, temperature limit controller 83 is made responsive to the temperature in the combustion chamber of the heater. This instrument is set for a maximum allowable temperature, such as 2600 F., and if for any reason the combustion zone temperature tends to exceed this limit. the instrument takes over the control of the fuel supply by controlling valve 77. In other words, instrument 83 is an over-control for instrument 76 and is a safety feature for protection of the heater and pebbles.

During operation of the pebble heater unit, it is essential to maintain a proper pressure differential between gases in heater 11 and reactor 12 in order to prevent any substantial flow of gases from one chamber to the other. A pressure differential controller 84 in communication with the gases in heater 11 and in reactor 12 continually records pressure differential between these points and maintains a suitable predetermined pressure differential therebetween by operating stack damper 85 in stack in response to variations from this predetermined pressure differential. Any low pressure differential from 0 to 25 inches of water, for example, may be used without substantial ow of gas from chamber to chamber. A higher pressure may be maintained in either the heater or the reactor, but when processing hydrocarbons, it is desirable to operate with a very low pressure differential in favor of the pebble heater chamber so that any tendency for gas to ow between the chambers is from the reactor to the heater.

As stated heretofore, the flow of pebbles thru the heater and reactor is controlled by a pebble feeder 17. This feeder may be of any conventional type or it may be a table feeder such as that shown in Figure II. Feeder 17 may be operated at a constant rate or the rate may be varied in order to maintain a product of constant specific gravity. The pebble flow thru the system is measured by instrument 86 which may be a recording ammeter, or wattmeter, on the motor actuating the pebble elevator.

The instrument is conveniently calibrated to read in I tons per hour.

The invention provides an effective snuff system for safety and protection of the apparatus. The control instruments enumerated are operated by compressed air, each being connected to `air supply line 91. The snuff system operates automatically in case of a failure of air supply at any point in the line and it may be operated manually from snuff switches 92 and 93 positioned at any convenient points about the installation. These switches operate valves 94 and 95 which shut off air and vent the air line 91 thru line 96. Failure of the air supply in line 91 or operation of switches 92 or 93 also operates switch 97 which may be any type of pressure actuated switch, thereby cutting ott electrical power to the unit motors (not shown). Upon failure of the air supply or upon operation of switches 92 or 93, valve 94 closes and valve 95 opens venting instrument air line to atmosphere. This closes valve 98 shutting off fuel supply to burner 21, and controls 28, 71, 48, 42, S6, S7, and 79 are actuated to close the valves which they operate. Con trol 28 closes valve 27 shutting off the ow of hydrocarbon feed to reactor 12; control 71 closes valve 31 shutting olf the flow of feed steam to line 26; control 48 closes valve 49 shutting ofr the supply of pressure maintenance gas in line 51; control 42 closes valve 43 discontinuing the operation of the blower 4l; control 56 closes valve 37 discontinuing the llow of quenching fluid in line 36; control 57 closes valve 58 shutting off the flow of water in line 59; and control 79 closes valve 81, thereby discontinuing the flow of steam thru line 78 to the turbine actuating air blower 24 which shuts ofi the air supply to burner 21. Likewise, valve 74 in line 73 and valve 80 in line 72 yare opened admitting steam to reactor 12 via line 26 and to heater 11 via line 22. Upon actuation ot the snuff system, control 69 which normally functions tu maintain valve 70 partially open, now opens this valve completely, thereby, permitting rapid purging of reactor 12. Control 84 opens stack damper 85 completely, allowing rapid purging of heater 11. Controls 45 and 53 open valves 46 and 54 respectively, thereby permitting the purge gas to bypass blower 41 and pass to the atmosphere via lines 47 and 55.

Figure ll shows some of the construction detail of pebble heater 11 and reactor 12, pebble ow thru the unit, and arrangement of apparatus for control of pebble feeder 17 in response to variations in the gravity of the product stream in line 39 from a predetermined specific gravity thru gravitometer controller 76. Corresponding parts in. Figures I and 1I are correspondingly numbered for simplicity and some of these parts need not be referred to again in connection with Figure 1I. Heater 11 has a suitable refractory lining 101. A mass of pebbles 102 is supported by a refractory arch 103 which is supported a substantial distance above the bottom of the heater, thereby providing an annular combustion space 104 below the refractory arch. Holes 105 in this retractory arch are provided for flow of hot combustion gas upwardly thru the pebble bed in the heater. While Figure I shows a single burner, a plurality of tangentially or upwardly tired burners may be utilized, in fact more uniform and efficient heating is obtained from the use of a plurality of burners. Reactor 12 is also lined with a high temperature refractory 106. A mass of pebbles 107 in reactor 12 passes downwardly over a series of gas distributing means made up of inverted troughs 108 supported at different levels on a series of annularly arranged tubes 109 which are attached to a flanged funnel 111. This funnel is supported by a ring member 112 which is removably attached to the shell of the reactor. Ring member 112 can be replaced by rings of other heights in order to vary the distance of flow of the reactants thru the reactor, thereby, making the reactor more adaptable to the various types of conversion processes. The neck of funnel 111 extends into and is in slidable relation with pebble conduit 16 leading from the reactor in order to accommodate various positions of funnel 111.

The arrangement illustrated in Figure II provides for a different control of the heat input to reactor 12 than that shown in Figure l. In this arrangement, a pyrometer or thermocouple 113 responsive to pebble temperature in throat 13 aetuates temperature control instrument 99, which in turn regulates the flow of fuel thru line 22 by operating valve 77. This control functions to maintain a relatively uniform predetermined temperature in the pebble stream as it enters reactor 12. Gravitometer instrument 76 regulates the speed of motor 115 which communicates thru a speed reducer 116 to the shaft of pebble feeder i". Any deviation in the gravity of the product stream from a suitable predetermined specific gravity is reflected thru instrument 76 in a variation in the speed of pebble feeder 17 and, therefore, in the rate of flow ol pebbles thru the unit. This variation in rate of flow of pebbles provides for maintaining a relatively uniform product with the usual variations in operating conditions.

The invention described herein is applicable to all hydrocarbon conversion processes in which the charge stock undergoes a change in specific gravity. It has particular utility in the cracking of light paraflinic hydrocarbons to produce olens.

ln a specific application of the invention, a hydrocarbon feed gas having the following composition by weight percent:

Methane 2.6 Ethane 21.6 Propane 74.5 Butanes and heavier 1.3

is processed in apparatus arranged according to Figure l at the rute of 1,647,000 cubic feet per day. The feed stream is crncsed at approximately i709" lr. to yield nn olen-rich etTlucnt comprising 2,950,000 standard cubic feet of gas of the following composition by weight percent:

The (ccd gas is introduced at approximately atmospheric temperature and the elllucnt from the reactor at n temperature ot about l700 F. is given a fast primary quench with water to a temperature of about 600 F. A secondary quench with water at atmospheric temperalure reduces the temperature ot the eilluent hydrocarbon stream to about 140 F'. for handling in the hydrocarbon blower which sends the product stream to the compressors. During operation the blower 41 maintains a relatively constant pressure of 4.2 p. s. i. g. in the upper portion of the reactor and a pressure of between 1.7 and 2.3 p. s. i. g. just upstream of the blower. Instrument 84 maintains a differential pressure of about 2 to 3 inches of water between the lower portion of heater 11 and upper portion oi reactor 12. The gravity of the product varies during operation from about .(95 to about .705 with the instrument set for control :it .Til specific gravity. With relatively uniform 7,256" alumina pebbles7 the pebble stream temperature entering the reactor varies from about 1950" to about 2000" F. due to slight iluctuations in operating conditions which are reflected in minor variations in specific gravity of the product with concomitant control ol` fuel input to burner 2l automatically effected in order to reestablish the predetermined specilic gravity of .7U preferred in the specific process described.

The specific application recited is not intended to limit the invention to the specic conditions disclosed therein. Reactirn temperatures may be varied from about l500 to about 350W F. according to the particular process involved and the design of the apparatus. While operating pressures iu thc reactor bctuccn atmospheric and about lil p. s. i. g. are prcterred, the use of other pressures is not outside the scope of the invention. The charge may be preheated to any convenient temperature from room temperature up lo a temperature approaching reaction temperature. ln general, the invention is not limited to any specific set of processing conditions but has broad application to hydrocarbon conversion reactions involving u change in specific gravity of the charge stock.

Pebble licctcr technique offers a number of advantages in processing hydrocarbons and particularly in cracking paratiinc hydrocarbons to produce olens where extremely sharp heating adds to the yield of desirable product. Heating rates of from 50 to 100 times as fast as are obtained by other methods are feasible in a well designed pebble heater without substantial contamination of tbe product streams with combustion gases. Such fast heat trg rates made available by pebble heater technique not only reduce undesirable side reactions in hydrocarbons cracking processes with concomitant increase in yield ol desirable product, but also afford extremely high capacity Vtor a unit of u given size in comparison to conventional apparatus of similar size. The present invention makes a valuable contribution to the hydrocarbon conversion art Il l) by providing accurate controls on pebble heater apparatus designed for use in this art.

I claim:

1. A process for Conversion of hydrocarbons at elevated temperatures in vapor phase, involving a change in specific gravity of said hydrocarbon, which comprises passing downwardly a continuous mass of hot pebbles thru a series of zones comprising at lea a pebble heating zone and a conversion Zone, feeding a stream of fuel and a stream of @typen-containing gas into a combustion zone adjacent said pebble heating zone thereby producing a combustible mixture, burning said mixture and passing resulting combustion gases thru said pebble heating zone in direct contact with said pebbles thereby heating them to substantially above a predetermined conversion temperature, contacting said column of pebbles in said com version zone with a stream of hydrocarbons under such conversion conditions as to obtain a product of prede termined specific gravity, quenching conversion products from said conversion zone to a relatively low predetermined temperature by direct contact with a suitable lluid stream, regulating the flow rate of said fluid stream in response to deviations from said predetermined tem pcraturc thereby maintaining relatively uniform product temperature, maintaining a relatively uniform pressure in the hydrocarbon feed stream, maintaining and regulating suction pressure in the stream of conversion products downstream from said quenching step so as to maintain a predetermined suitable pressure between about atmospheric and about 50 p. s. i. g. in said conversion zone, maintaining a gas pressure in said pebble heating zone slightly below the pressure in said conversion zone thereby preventing llow of gases from said pebble heating zone to said conversion zone, and maintaining a relatively uniform pebble flow rate.

2. A process for conversion of hydrocarbons at elevated temperatures in vapor phase, involving a change in specic gravity of said hydrocarbon, which comprises passing downwardly a continuous mass of hot pebbles thru a series of zones comprising at least a pebble heat ing zone and a conversion zone, contacting that portion of said continuous mass of pebbles in said pebble heating zone with a stream of hot combustion gas thereby heating same to substantially `above a predetermined conversion temperature, contacting that portion of said mass of pebbles in said conversion zone with a stream of hydrocarbons under such conversion conditions as to obtain an eluent of predetermined specic gravity, quenching said effluent to a relatively low predetermined temperature by direct Contact with a suitable lluid stream, regulating the flow rate of said Huid stream in response to deviations from said predetermined temperature thereby maintaining relatively uniform product temperature, determining the specific gravity of tbe vaporous cllluent by comparing the weight of same with the weight of an equal volume of air, and substantially maintaining said predetermined specie gravity by `regulating the heat input to said conversion zone in response `to variations from said predetermined spe-cie gravity.

3. A process for conversion of hydrocarbons at elevated temperatures in vapor phase, involving a change in specific gravity of said hydrocarbon, which comprises passing downwardly a continu-ous mass oi hot pebbles thru a series of zones comprising at least a pebble heating zone and a conversion zone, feeding a stream of fuel and a stream of oxygen-containing gas into a combustion zone adjacent said pebble heating zone thereby producing a combustible mixture, burning said mixture and passing resulting combustion gases thru said pebble heating zone in direct Contact with said pebbles thereby heat ing them to substantially above a predetermined conversion temperature, contacting said column of pebbles in said conversion zone with a stream of hydrocarbons under such conversion conditions as to obtain a product of predetermined specific gravity, quenching conversion products from said conversion zone to a relatively low predetermined temperature by direct contact with a suitable fluid stream, regulating the flow rate of said uid stream in response to deviations from said predetermined temperature thereby maintaining relatively uniform product temperature, maintaining a relatively uniform pressure in the hydrocarbon feed stream, maintaining and regulating suction pressure in the stream of conversion products downstream from said quenching step so as to maintain a predetermined suitable pressure between about atmospheric and about 50 p. s. i. g. in said conversion zone, maintaining a gas pressure in said pebble heating zone slightly below the pressure in said conversion zone thereby preventing flow of gases from said pebble heating zone to said conversion zone, determining the specific gravity of the vaporous product by comparing the weight of same with the weight of an equal volume of air, substantially maintaining said predetermined specie gravity by regulating the rate of fuel input to said combustion zone in response to deviations from said predetermined speciic gravity, and maintaining a relatively uniform pebble ow rate.

4. A process for conversion vated temperatures in vapor phase, involving a change in specific gravity of said hydrocarbon, which comprises passing downwardly a continuous mass of hot pebbles thru a series of zones comprising at least a pebble heating zone and a conversion zone, c-ontacting that portion of ,said continuous mass of pebbles in said pebble heating zone with a stream of hot combustion gas thereby heating same to substantially above a predetermined conversion temperature, contacting that portion of said mass of pebbles in said conversion zone with a stream of hydrocarbons under such conversion conditions as to obtain an eflluent of predetermined specific gravity, quenching said effluent to a relatively low predetermined temperature by direct contact with a suitable uid stream, regulating the flow rate of said iiuid stream in response to deviations fr-om said predetermined temperature thereby maintaining relatively uniform product temperature, dctermining the specific gravity of the vaporous eilluent by comparing the weight of same with the weight of an equal volume of air, and substantially maintaining said predetermined specilic gravity by regulating the rate of flow of said pebble mass thru said conversion zone in respouse to deviations from said predetermined specific gravity.

5. A process vated temperatures in vapor phase, in specic gravity of said hydrocarbon, passing a downwardly moving column of hot recycled pebbles thru a series of zones comprising at least a pebble heating zone and a conversion zone; feeding a stream of and a stream of oxygen-containing gas into a combustion zone adjacent said pebble heating zone thereby producing a combustile mixture; burning said mixture and passing resulting combustion gases thru said pebble heating zone in direct contact with said pebbles thereby heating them to substantially above a predetermined conversion temperature; contacting said column of pebbles in said conversion zone with a stream of hydrocarbons under such conversion conditions as to obtain a product of predetermined gravity; regulating the heat input to said conversion zone in response to variations from said predetermined gravity; quenching conversion products from said conversion zone to a relatively low predetermined temperature by direct Contact with a suitable liquid stream; regulating the How rate of said liquid stream in response to deviations from said predetermined temperature thereby maintaining relatively uniform product temperature; maintaining a relatively uniform pressure in the hydrocarbon feed stream; maintaining a predetermined pressure between atmospheric and about 50 p. s. i. g. in said conversion zone by correlating pressure in the product stream downstream from said quenching of hydrocarbons at elefor conversion of hydrocarbons at eleinvolving a change which comprises i zone with the pressure in said hydrocarbon feed stream by a series of successively and cumulatively functioning steps comprising varying, within a limited range, the rate of ow of said product stream in a flow control zone downstream of said quenching zone, recycling a portion of said product stream from downstream of said liow control zone to upstream thereof when said limited range of variance is insulhcient to maintain said predetermined pressure, finally, admitting a separate stream of pressuremaintenance gas t0 said product stream upstream of said flow control zone when the pressure therein approaches atmospheric as a lower limit; maintaining the gas pressure in said pebble heating zone slightly below the pressure in said conversion zone; and maintaining relatively uniform pebble ow rate.

6. A process for conversion of hydrocarbons at elevated temperatures in vapor phase, involving a change in specific gravity of said hydrocarbon, which comprises passing a downwardly moving column of hot recycled pebbles thru a series of zones comprising at least a pebble heating zone and a conversion zone; feeding a stream of fuel and a stream of oxygen-containing gas into a combustion zone adjacent said pebble heating zone thereby producing a combustible mixture; burning said mixture and passing resulting combustion gases thru said pebble heating zone in direct contact with said pebbles thereby heating them to substantially above a predetermined conversion temperature; contacting said column of pebbles in said conversion zone with a stream of hydrocarbons under such conversion conditions as to obtain a product of predetermined gravity; regulating the heat input to said conversion zone in response to variations from said predetermined gravity; quenching conversion productsk from said conversion zone to n relatively low predetermined temperature by direct contact with a suitable liquid stream; regulating the ilow rate of said liquid stream iu response to deviations from said predetermined temperature thereby maintaining relatively uniform product temperature; maintaining a relatively uniform pressure in the hydrocarbon feed stream; maintaining a predetermined pressure between atmospheric and about 5G p. s. i. g. in said conversion zone by correlating pressure in the product stream downstream from said quenching zone with the pressure in said hydrocarbon feed stream by a series of successively and cumulatively functioning steps comprising varying, within a limited range, the rate of flow of said product stream in a flow control zone downstream of said quenching zone, recycling a portion of said product stream from downstream of said tiow control zone to upstream thereof when said limited range of variance is insufficient to maintain said predetermined pressure, finally, admitting a separate stream of pressure-mainlenance gas to said product stream when the pressure therein approaches atmospheric as a lower limit; maintaining the gas pressure in said pebble heating zone slightly below the pressure in said conversion zone by continuously measuring variations in differential between said pressures and substantially simultaneously adjusting the pressure in said pebble heating zone to restore the desired differential thereby preventing ow of gases from said pebble heating zone to said conversion zone', and maintaining relatively uniform pebble flow rate.

7. A process for conversion of hydrocarbons at elevated temperatures in vapor phase, involving a change in specic gravity of said hydrocarbon, which comprises passing a downwardly moving column of hot pebbles thru a series of zones comprising at least a pebble heating zone and la conversion zone; feeding a stream of fuel and a stream of oxygenacontaining gas into a combustion zone adjacent said pebble heating zone thereby producing a combustible mixture; burning said mixture and passing resulting combustion gases thru said pebble heating zone in direct contact with said pebbles thereby heating them to substantially above a predetermined conversion ternperature; contacting said column of pebbles in said conversion zone with a hydrocarbon stream under such conversion conditions as to obtain a product of predetermined gravity; quenching conversion products from said conversion zone to a relatively low predetermined temperaturc by direct contact with a suitable liquid stream; regulating the ow rate of said liquid stream in response to deviations from said predetermined temperature thereby maintaining relatively' uniform product temperature; determining the specific gravity of the vaporous product by comparing the weight of same with the weight of un equal volume of air; maintaining said predetermined gravity of the product stream by regulating the rate of fuel input to said combustion zone in response to variations from said predetermined gravity; maintaining a relatively uniform pressure in the hydrocarbon feed stream; maintaining a predetermined pressure between atmospheric and about 50 p. s. i. g. in said conversion zone by correlating pressure in the product stream downstream from said quenching zone with the pressure in said hydrocarbon feed stream by a series of successively and cumulativcly functioning steps comprising varying, within a limited range, the rate of ow of said product stream in n flow control zone downstream of said quenching zone, recycling u portion of said product stream from downstream of said flow control zone to upstream thereof when said limited range ot variance is insutiicient to maintain said predetermined pressure, and finally, admitting a separate stream of pressure-maintenance gas to said product stream when the pressure therein approaches atmospheric as a lower limit; maintaining the gas pressure in said pebble heating zone slightly below the pressure in said conversion zone; and maintaining relatively uniform pebble flow rate.

8. A process for conversion of a hydrocarbon material at an elevated temperature which comprises passing a downwardly moving column of hot pebbles thru a series of zones comprising at least a pebble heating zone and a conversion zone; feeding a stream of fuel and a stream of oxygen-containing gas into a combustion zone adjacent said pebble heating zone thereby producing a combustible mixture: burning said mixture and passing resulting combustion gases thru said pebble heating zone in direct contact with said pebbles thereby heating them to substantially above a predetermined conversion temperature; contacting said column of pebbles in said conversion zone with :i stream of hydrocarbons under such conversion conditions as to obtain a product of predetermined gravity; quenching conversion products from Said conversion zone to a relatively low predetermined temperature by direct Contact wtih a suitable liquid stream; regulating the flow rate of said liquid stream in response to deviaw tions from said predetermined temperature thereby maintaining rietivcly uniform product temperature; determining the specific gravity of the vaporous product by comparing the weight of same with the weight of an equal volume of air; maintaining said predetermined gravity of the product stream by regulating the rate of fuel input to said combustion zone in response to variations from said predetermined gravity; maintaining a relatively uniform pressure in the hydrocarbon feed stream; maintaining n predetermined pressure between atmospheric and about F0 p. s i. g. in said conversion zone by correlating pressure in the product stream downstream from said preaching zone with the pressure in said hydrocarbon feed stream t; a series oi successively and cumulativcly lunctiuning steps comprising varying, within a limited range. thc rate of tiow of said product stream in a flow control zone downstream of said quenching zone, recycling a portion ot' said product stream from downstream of said flow control zone to upstream thereof when said limited range of variance is insufficient to maintain said predetermined pressure, and finally, admitting a separate stream of pressure-maintenance gas to said product stream when the pressure therein approaches atmospheric as a lower limit; maintaining the gas pressure in said pebble heating CII liti

zone slightly below the pressure in said conversion zone by continuously measuring variations in differential in said pressures and substantially simultaneously adjusting the pressure in said pebble heating zone to restore the desired differential thereby preventing fiow of gases from said pebble heating zone to said conversion zone; and maintaining relatively uniform pebble How rate.

9. A pebble heater system for etecting hydrocarbon conversion in the vapor phase involving a change in specic gravity comprising in combination a series of substantially vertically extending chambers including a pebble heating chamber, a conversion chamber positioned below said pebble heating chamber, and a relatively narrow interconnecting neck, said chambers and neck enclosing a continuous fiuent mass of pebbles; a pebble inlet in the upper portion of said pebble heating chamber; a pebble outlet in the lower portion of said conversion chamber; means for transferring pebbles from said outlet to said inlet; supply and discharge means leading to and from said pebble heating chamber for supplying hot combus tion gas thereto and removing cooled gas therefrom; a feed line communicating with the lower portion of said conversion chamber; an effluent line communicating with the upper portion of said conversion chamber; means for injecting a quenching uid into said eluent line; and means in said eiluent line downstream of said last named means for applying suction pressure therein and correlating the same with pressure in said feed line in order to maintain a substantially uniform predetermined pressure in said conversion chamber, said means comprising a blower having speed controlling means responsive to variations in upstream pressure from a suitable predetermined pressure, a valved recycle line communicating from a point downstream to a point upstream of said blower said valve being operated by a control means responsive to said upstream pressure, and a valved line for introducing pressure-maintenance gas into said effluent line at a point between said blower and said quenching means to a suitable predetermined minimum pressure in said effluent line.

10. A pebble heater system for etlecting hydrocarbon conversion in the vapor phase involving a change in Spccic gravity comprising in combination a series of substantially vertically extending chambers including a chamber; means for transferring pebbles from said outlet to said inlet; supply `and discharge means leading to and from said pebble heating chamber for supplying hot combustion gas thereto and removing cooled gas therefrom; a feed line communicating with the lower portion of said being operated by a control means responsive to said upstream pressure, and a valved line for introducing prescontroller-recorder means sensitive to pressure differentials, having communication with the lower portion of said pebble heating chamber, and with the effluent line adjacent said conversion chamber, and with a damper control means in said discharge means leading from said pebble heating chamber and being adapted for maintaining a predetermined pressure differential between the gases in said conversion chamber and in said pebble heating chamber.

l1. A process for conversion of hydrocarbons at elevated temperatures in vapor phase, involving a change in specific gravity of said hydrocarbon, which comprises passing downwardly a continuous mass of hot pebbles thru a series of zones comprising at least a pebble heating zone and a conversion zone, contacting that portion of said continuous mass of pebbles in said pebble heating zone with a stream of hot combustion gas thereby heating same to substantially above a predetermined conversion temperature, contacting that portion of said mass of pebbles in said conversion zone with a stream of hydrocarbons under such conversion conditions as to obtain an effluent of predetermined specific gravity, quenching said efuent to a relatively low predetermined temperature by direct contact with a suitable uid stream, regulating the flow rate of said uid stream in response to deviations from said predetermined temperature thereby maintaining relatively uniform product temperature, determining the specific gravity of the vaporous elliuent, and substantially maintaining said predetermined specific gravity by regulating the heat input to said conversion zone in response to variations from said predetermined specific gravity.

l2. A process for conversion of hydrocarbons at elevated temperatures in vapor phase, involving a change in specilic gravity of said hydrocarbon, which comprises passing downwardly a continuous mass of hot pebbles thru a series of zones comprising at least a pebble heating zone and a conversion zone, contacting that portion of said continuous mass of pebbles in said pebble heating zone with a stream of hot combustion gas thereby heating same to substantially above a predetermined conversion temperature, contacting that portion of said mass of pebbles in said conversion zone with a stream of hydrocarbons under such conversion conditions as to obtain an eiuent of predetermined specific gravity, quenching said effluent to a relatively low predetermined temperature by direct contact with a suitable uid stream, and regulating the flow rate of said fluid stream in response to deviations from said predetermined temperature thereby maintaining relatively uniform product temperature.

13. pebble heater system for eiecting hydrocarbon conversion 1n the vapor phase involving a change in speclfic 'grav1ty comprising in combination a series of substantially vertically extending chambers including a pebble heating chamber, a conversion chamber positioned below said pebble heating chamber, and a relatively narrow interconnecting neck, said chambers and neck enclosing a continuous fluent mass of pebbles; a pebble inlet 1n the upper portion of said pebble heating chamber; a pebble outlet in the lower portion of said conversion chamber; means for transferring pebbles from said outlet to said inlet; means for introducing a hot gas to said pebble heating chamber and means for withdrawing cooled gas therefrom; a gas inlet line and a gas outlet line in said conversion chamber; a quench line in said gas outlet line having a flow control valve therein; a temperaturecontroller communicating with said valve and with said outlet line downstream of said quench line; and a gravitometer-controller element sensitive to the specific gravity of the vaporous conversion chamber effluent and adapted io as to regulate the heat input to said conversion cham- 14. A pebble heater system for effecting hydrocarbon conversion in the vapor phase involving a change in specific gravity comprising in combination a series of substantially vertically extending chambers including a pebble heating chamber, a conversion chamber positioned below said pebble heating chamber, and a relatively narrow interconnccting neck, said chambers and neck enclosing a continuous fluent mass of pebbles; a pebble inlet in the upper portion of said pebble heating chamber; a pebble outlet in the lower portion of said conversion chamber; means for transferring pebbles from said outlet to said inlet; a combustion chamber in communication with said pebble heating chamber having an air supply line and a fuel supply line; a feed line and an efliuent line each communicating with said conversion chamber; a quench tank in said eluent line; a quench line leading into said quench tank having a ow control valve therein; a temperaturecontroller communicating with said valve and with said etiluent line downstream of said quench tank; and a gravitometer-controller element sensitive to the specific gravity of the vaporous conversion chamber effluent in communication with said effluent line and with said fuel supply line and adapted so as to regulate the flow rate of fuel in response to variations from a predetermined specific gravity of the vapor fraction of said efliuent.

l5. A pebble heater system for effecting hydrocarbon conversion in the vapor phase involving a change in specific gravity comprising in combination a series of substantially vertically extending chambers including a pebble heating chamber having means for passing a hot gas therethru, a conversion chamber positioned below said pebble heating chamber and having a gas inlet line and an effluent line, and a relatively narrow interconnecting neck, said chambers and neck enclosing a continuous fluent mass of pebbles; a quench tank in said eiiluent line; `a quench line leading into said quench tank having a flow control valve therein; a temperature-controller communieating with said valve and with said eluent line downstream of said quench tank; means for returning pebbles from an exit in the lower portion of said conversion charnber to an inlet in the upper portion of said pebble heating chamber, including a pebble feeder adapted so as to feed pebbles at a regulable rate thru said return means; and a gravitometer-controller element sensitive to the specie gravity of the vaporous effluent hydrocarbons from said conversion chamber in communication with and adapted so as to regulate said pebble feeder, thereby varying the heat input to said conversion chamber.

16. A pebble heater system for effecting hydrocarbon conversion in the vapor phase involving a change in specific gravity comprising in combination a series of substantially vertically extending chambers including a pebble heating chamber, a conversion chamber positioned below said pebble heating chamber, and a relatively narrow interconnecting neck, said chambers and neck enclosing a continuous fluent mass of pebbles; a pebble inlet in the upper portion of said pebble heating chamber; a pebble outlet in the lower portion of said conversion chamber; means for transferring pebbles from said outlet to said f inlet; a combustion chamber in communication with said pebble heating chamber having an air supply line and a fuel supply line; a feed line and an effluent line each com municating with said conversion chamber; a quench tank in said effluent line; a quench line ieading into said quench tank having a ow control valve therein; a temperaturecontroller communicating with said valve and with said effluent line downstream of said quench tank; a gravitometercontroller element sensitive to the specific gravity of the vaporous conversion chamber effluent in communication with said eftluent line and with a ow control means in said fuel supply line and adapted to regulate the flow rate of fuel in response to variations from a predetermined specific gravity ot said eiuent; and a ow control element responsive to said flow rate of fuel arranged so as to correlate air supply in said air supply line with said fuel flow rate.

17. A pebble heater system for effecting hydrocarbon conversion in the vapor phase involving a change in specific gravity comprising in combination a series of substantially vertically extending chambers including a pebble heating chamber, a conversion chamber positioned below said pebble heating chamber, and a relatively narrow interconnecting neck, said chambers and neck enclosing a continuous fluent mass of pebbles; a pebble inlet in the upper portion of said pebble heating chamber; a pebble outlet in the lower portion of said conversion chamber; means for transferring pebbles from said outlet to said inlet; means for introducing a hot gas to said pebble heating chamber and means for withdrawing cooled gas therefrom: a gas inlet line and a gas outlet lin: in said conversion chamber; a quench line in said gas outlet line having a ow control valve therein; and a temperature-controller communicating with said valve and with said outlet line downstream of said quench line.

18. A pebble heater system for effecting: hydrocarbon conversion in the vapor phase kinvolving a change in specilic gravity comprising in combination a series of substantially vertically extending chambers including a pebble heating chamber. a conversion chamber positioned below said pebble heating chamber, and a relatively narrow iuterconnecting neck, said chambers and neck enclosing fluent mass of pebbles; a pebble inlet in the upper portion of said pebble heating chamber; a pebble outlet in the louter portion of said conversion chamber; means for transferring pebbles from said outlet to said inlet; a comA bustion chamber in communication with said pebble heating: chamber having an air supply line and a fuel supply line; a feed line and an etiluent line each communicating with said conversion chamber; a quench tank in said effluent line; a quench line leading `into said quench tank having a flow control valve therein; and a temperaturecontroller communicating with said valve and with said eiluent line downstream of said quench tank.

t9. A pebble heater system for effecting; hydrocarbon conversion in the vapor phase involving a change in spevic gravity comprising in combination a series of substantially vertically evtenrling chambers including a pebble heating chamber having means for passing a hot gas therethru. u conversion chamber positioned below said pebble heatintv chamber and having a gas inlet line and an effluent line, a relatively narrow intercmmecting neck, said chambers and neck enclosing a. continuous fluent mass of ebbles; a quench tank in said etlluent line; a quench lin: leading into said quench tank having a ow control valve therein: a tcmperatiue-i:onti'oller communi eating with said valve and with said eluent line downstream of seid quench tank: and ineens for returning pebbles from an exit in the lower portion ot' said conversion chamber to an inlet in the upper portion of said pebble heating chamber. including a pebble feeder adapted so as to [ccd pebbles at a regulable rate thru said return means.

2l?. A pebble beater system for elfecting hydrocarbon conversion in the vapor phase involving a change in specific gravity comprising in combination a series of substantially vertically extending chambers including a pebble heating chamber, a conversion chamber positioned below said pebble beating chamber, and a relatively narrow interconnecting neck. said chambers and neck enclos` ing a continuous tluent mass of pebbles; a pebble inlet in the upper portion oi said pebble heating chamber; a pebble outlet in the lower portion of said conversion chamber: means for transferring pebbles from said outlet to said inlet; a combustion chamber' in communication willi said pebble heating chamber having an air supply line and a fuel supply line; a feed line and an eilluent line cach communicating with said conversion chamber; u quench tank in said ellluent line; a quench line leading into said quench tank having a flow control valve therein; :t temporalurecontrollcr communicating with said valve and with said eflluent line downstream of said quench tank; and a .tlow control element responsive to the flow rate of fuel arranged so as to correlate air supply in said ai.' supply line with said fuel llow rate.

till

21. A snuling system for use in combination with pebble heater apparatus having a pebble heating chamber, a conversion chamber positioned below said pebble lheating chamber, a relatively narrow interconnecting chamber between said chambers enclosing a continuous fluent mass of pebbles, means for returning pebbles from an exit in the lower portion of said conversion chamber to an inlet in the upper portion of said pebble heating chamber, fuel and air lines communicating with the lower portion of said pebble heating chamber, a feed supply line and an effluent line communicating with said conversion chamber, and a line for supplying a purge gas to said conversion chamber, said snuting system comprising a series of fluid pressureactuated flow control valves positioned in said fuel, feed, aud purge gas lines, each cornmunieating with a huid supply line having pressure release means, said valves functioning below a predetermined minimum pressure in said .fluid supply line so as to simultaneously discontinue flow of fuel to said pebble heating chamber, flow of feed to said conversion chamber, and to pass purge gas thru said conversion chamber.

22. A snuftng system for use in combination with pebble heater apparatus having a pebble heating chamber, a conversion chamber positioned below said pebble heating chamber', a relatively narrow interconnecting chamber between said chambers enclosing :t continuous fluent mass of pebbles, means for returning pebbles from an exit in the lower portion of said conversion chamber to an inlet in the upper portion of said pebble heating chamber, fuel and air lines communicating with the lower portion of said pebble heating chamber, a feed supply line and an effluent line communicating with said conversion chamber, and a line for supplying a purge gas to said conversion chamber, said snuiug system comprising a series of fluid pressure-actuated flow control valves positioned in said fuel, air, feed, and purge gas lines, each communieating with a fluid supply line having pressure release means, said valves Functioning below a predetermined minimum pressure in said fluid supply line so as to simultuneously discontinue flow of fuel and air to said pebble heating chamber, ilow of feed to said conversion chamber, and to pass purge gas thru said conversion chamber.

23. A snuing system for use in combination with pebble heater apparatus having a pebble heating chamber, a conversion chamber positioned below said pebble heating chamber, a relatively narrow interconnecting chamber between said chambers enclosing a continuous fluent mass of pebbles, means for returning pebbles from an exit in the lower portion of said conversion chamber to an inlet in the upper portion of said pebble heating chamber, fuel and air lines communicating with the lower portion of said pebble heating chamber, a feed supply line and an ellluent line communicating with said conversion chatnber, a line for supplying a purge gas to said conversion chamber` a quench tank in said eluent line having a quench tluid inlet line and a quenched product effluent line, said snufling system comprising a series of fluid pressure-actuated tlow control valves positioned in said fuel, feed, quench fluid, and purge gas lines, each communicating with a fluid supply line having pressure release means, said valve functioning below a predetermined minimum pressure in said liuid supply line so as to simultaneously discontinue flow of fuel to said pebble heating chamber, flow of feed to said conversion chamber, flow of quench fluid to said quench tank, and to pass purge gas thru said conversion chamber.

24. A snulling system for use in combination with pebble heater apparatus having a pebble heating chamber, a conversion chamber positioned below said pebble heating chamber, a relatively narrow interconnecting chamber between said chambers enclosing a continuous fluent mass of pebbles, means for returning pebbles from an exit in the lower portion of said conversion chamber to an inlet in the upper portion of said pebble heating chamber, fuel and air lines communicating with the lower portion of said pebble heating chamber, a feed supply line and an eiliuent line communicating with said conversion chamber, a line for supplying a purge gas to said conversion chamber, a quench tank in said eluent line having a quench fluid inlet line and a quenched product effluent line, variable means in said quenched effluent line for maintaining a suction pressure on said line having a power supply line thereto, said snuing system comprising a series of uid pressure-actuated ow control valves positioned in said fuel, feed, quench uid, power supply, and purge gas lines, each communicating with a fluid supply line having pressure release means, said valves functioning below a predetermined minimum pressure in said fluid supply line so as to simultaneously discontinue iiovv of fuel to said pebble heating chamber, ow of feed to said conversion chamber, ow of quench fluid to said quench tank, power to said variable means, and to pass purge gas thru said conversion chamber.

25. A snuiiing system for use in combination with peb-A ble heater apparatus having a pebble heating chamber, a conversion chamber positioned below said pebble heating chamber, a relatively narrow interconnecting chamber between said chambers enclosing a continuous fluent mass of pebbles, means for returning pebbles from an exit in the lower portion of said conversion chamber to an inlet in the upper portion of said pebble heating chamber, fuel and air lines communicating with the lower portion of said pebble heating chamber, a feed supply line and an effluent line communicating with said conversion chamber, a line for supplying a purge gas to said conversion chamber, a quench tank in said eHuent line having a quench uid inlet line and a quenched product efuent line, variable means in said quenched product efuent line `for maintaining a suction pressure on said line having a power supply line thereto, said snuiling system comprising a series of duid pressure-actuated ow control valves positioned in said fuel, air, feed, quench fluid, power supply, and purge gas lines, each communicating with a uid supply line having pressure release means, said valves functioning below a predetermined minimum pressure in said uid supply line so as to simultaneously discontinue flow of fuel and air to said pebble heating chamber, llow of feed to said Conversion chamber, ilow of quench fluid to said quench tank, power to said variable rneans, and to pass purge gas thru said conversion chamber.

References Cited in the le of this patent UNITED STATES PATENTS 2,345,272 I uhrs Mar, 2R, i944 2,390,03l Schutte et ai. Nov. 27, 1945 2,447,049 Bailey et al. Mar. ll, i947 2,503,188 Bergstrom Apr. 4, 1950 2,530,274 Weber Nov. 14, 1950 2,627,497 Robinson Feb. 3, 1953 2,643,216 Findlay June 23, 1953 

1. A PROCESS FOR CONVERSION OF HYDROCARBON AT ELEVATED TEMPERATURE IN VAPOR PHASE, INVOLVING A CHANGE IN SPECIFIC GRAVITY OF SAID HYCROCARBON, WHICH COMPRISES PASSING DOWNWARDLY A CONTINUOUS MASS OF HOT PEBBLES THRU A SERIES OF ZONES COMPRISING AT LEAST A PEBBLE HEATING ZONE AND A CONVERSION ZONE, FEEDING A STREAM OF FUEL AND A STREAM OF OXYGEN-CONTAINING GAS INTO A COMBUSTION ZONE ADJACENT SAID PEBBLE HEATING ZONE THEREBY PRODUCING A COMBUSTIBLE MIXTURE, BURNING SAID MIXTURE AND PASSING RESULTING COMBUSTION GASES THRU SAID PEBBLE HEATING ZONE IN DIRECT CONTACT WITH SAID PEBBLE THEREBY HEATING THEM TO SUBSTANTIALLY ABOVE A PREDETERMINED CONVERSION TEMPERATURE, CONTACTING SAID COLUMN OF PEBBLES IN SAID CONVERSION ZONE WITH A STREAM OF HYDROCARBONS UNDER SUCH CONVERSION CONDITIONS AS TO OBTAIN A PRODUCT OF PREDETERMINED SPECIFIC GRAVITY, QUENCHING CONVERSION PRODUCTS FROM SAID CONVERSION ZONE TO A RELATIVELY LOW PREDETERMINED TEMPERATURE BY DIRECT CONTACT WITH A SUITABLE FLUID STREAM, REGULATING THE FLOW RATE OF SAID FLUID STREAM 